1. Field of the Invention
This invention relates to an apparatus for determining the sag of a running web of material transversely to its longitudinal direction.
2. Description of Prior Art
For determining the characteristics of a running web of material, for example for the purpose of subjecting the web to a further treatment in accordance with the determined characteristics, it may be necessary to measure the sag of the web transversely to its running direction Such a measurement of the sag is for example, required in the method for the reduction of the sag of a flattened tubular film web of thermoplastic material, produced by blow molding, transversely to its longitudinal direction, as described in U.S. patent application Ser. No. 07/709,319 now pending. The methods as described in said patent application for the reduction of the sag are made use of according to the size of the measured sag.